Hydraulic braking energy utilization for emergency steering, braking, charging accumulator(s), and/or work functions to reduce or prevent engine from overspeed, assist acceleration and/or unlimited towing

The present invention is a continuation of U.S. application Ser. No. 18/198,647 filed May 17, 2023, which in turn is a continuation of U.S. application Ser. No. 17/350,799 filed Jun. 17, 2021 (now U.S. Pat. No. 11,674,532), which in turn is a continuation of U.S. application Ser. No. 16/184,195 filed Nov. 8, 2018 (US U.S. Pat. No. 11,156,237), which in turn claims priority on U.S. Application Ser. No. 62/583,298 filed Nov. 8, 2017, which are incorporated herein by reference.

The present disclosure is directed to a system and method configured to direct the braking energy from a high-pressure port at a propulsion motor side of a hydraulic circuit/system and to at least partially use such energy for (a) emergency steering and braking; (b) input into accumulator(s); and/or, (c) various other work functions. Moreover, the system and method of the present disclosure is configured to return hydraulic fluid (e.g., hydraulic fluid, etc.) back to the same port at the propulsion pump side when the motor is running as a pump. The motor may run as a pump, for example: (1) when the engine dies at high machine velocity on flat ground; (2) when the engine dies while the machine travels downhill; (3) during machine deceleration; and/or, (4) when the machine is being towed.

Systems and methods for controlling speed and braking in vehicles having hydrostatic drives are known in the art. During braking in some known hydrostatic drives, an associated motor gathers the vehicle's momentum and runs as a pump, while an associated pump runs as a motor. The input torque from the pump transfers to the vehicle's engine and can cause overspeed due to insufficient engine braking power. The more input torque, the more engine overspeed, and/or excessive overspeed can result in damage to the engine and the pump.

During braking in other known hydrostatic drives, a speed limiter circuit is utilized which converts excessive hydrostatic power to heat through a pressure-reducing valve. The heat energy is then dissipated to the ambient environment through the transmission housing or via an associated hydraulic fluid cooler. While this approach provides engine overspeed protection to a certain level, the heat energy dissipated to the ambient environment reduces overall system performance and efficiency. Examples of prior art speed control and hydrostatic drives are disclosed in U.S. Pat. Nos. 9,512,918 and 7,874,153, which are incorporated herein by reference.

Systems and methods for overcoming these prior art deficiencies related to speed and braking control in vehicles having hydrostatic drives are needed.

Non-limiting aspects of the present disclosure include a system and method configured to direct the braking energy in a propulsion circuit of a machine. More particularly, the braking energy is directed from a high-pressure port at the propulsion motor side of the circuit to be used in: (a) an emergency steering and braking circuit; (b) one or more accumulators; and/or (c) any other work functions performed by common components in machines which utilize propulsion circuits.

Moreover, in accordance with other non-limiting aspects of the present disclosure, the exemplary system and method are configured to return hydraulic fluid back to the same high-pressure port at the propulsion pump side when the motor is running as a pump. This may occur, for example, when: (1) the engine dies at high machine velocity on flat ground; (2) the engine dies while the machine is undergoing downhill travel; (3) the machine is decelerating; (4) the machine is being towed; and/or, (5) any other time the propulsion motor is being driven as a pump. Thus, the system and method of the present disclosure advantageously utilize braking energy to overcome the aforementioned deficiencies of the prior art.

In some non-limiting embodiments, braking energy can first be utilized for emergency steering and braking operations. In other non-limiting embodiments, braking energy can also or alternatively be stored in accumulators for later use. In additional non-limiting embodiments, braking energy can also or alternatively be utilized in any number of different types of work functions commonly performed by machines which utilize propulsion circuits. For example, braking energy can be at least partially utilized in different work functions to: (a) minimize heat (e.g., by avoiding the use of a pressure-reducing valve to dissipate the energy); (b) minimize engine overspeed (e.g., by reducing the pump side pressure at port B to a level that results in minimum input torque transferred to the engine); (c) assist in machine acceleration; (d) enable unlimited towing; and/or (c) limit steering during towing.

One non-limiting object of the present disclosure is to provide a hydraulic circuit which includes a pump configured to be driven by a prime motor. The circuit further includes a hydrostatic motor fluidly coupled to the pump by first and second lines (i.e., supply and return lines), one or more work function actuators or accumulators fluidly coupled with at least one of the first and second lines, and valving operative to direct at least a portion of pressurized fluid output from the motor during braking operations to at least one of the one or more work function actuators or accumulators. These exemplary non-limiting components thereby reduce or prevent the prime motor (i.e., engine) from over-speeding, as well as minimize heat generation in the hydraulic circuit.

The non-limiting hydraulic circuits disclosed herein can optionally further include a pressure-reducing valve for converting hydraulic energy to thermal energy, wherein the valving is further operative to direct pressurized fluid from the motor to the pressure-reducing valve during braking. Over-speeding in the prime motor is thereby prevented.

In accordance with other non-limiting aspects of the present disclosure, the exemplary hydraulic circuit is optionally at least one of a hydrostatic or open machine propel circuit. The hydrostatic propel circuit optionally includes a plurality of motors and pumps, and the plurality of motors include at least one of a fixed, 2-position, or proportional motor. The open-circuit propel system optionally includes a plurality of motors and one pump, and the plurality of motors include at least one of a fixed, 2-position, or proportional motor.

In accordance with other non-limiting aspects of the present disclosure, the one or more work function actuators optionally can include at least one work motor of a fan drive motor, a generator motor, cylinders, rotary actuators, or any motor that is loaded during engine dynamic braking. The work motor can be part of a fixed or variable pump system, open-circuit or closed-loop hydrostatic system. The hydraulic circuit optionally further includes a work function pump configured to be de-stroked to zero displacement, or dump its output to a reservoir, during engine dynamic braking. The hydraulic circuit optionally further comprises a micro-controller. The hydraulic circuit can optionally be used in a hydrostatic drive of a machine for propelling the machine.

In accordance with other non-limiting aspects of the present disclosure, there is provided a method of controlling a hydraulic drive of a machine, the hydraulic drive including a pump adapted to be driven by a prime motor of the machine, a motor fluidly coupled to the pump by first and second lines for propelling the machine, and at least one of a work function actuator or an accumulator fluidly coupled with at least one of the first and second lines. The method includes, during machine deceleration, directing at least a portion of pressurized fluid output from the motor to at least one of the work function actuator or the accumulator to thereby prevent the prime motor from over-speeding and to minimize heat generation in the hydraulic circuit.

In accordance with other non-limiting aspects of the present disclosure, there is provided a hydraulic circuit that uses the braking energy of a hydrostatic propulsion system for: (a) emergency steering; (b) braking; (c) charging accumulator(s); (d) one or more work functions to prevent the engine from overspeed and minimize heat generation; (c) assisting acceleration; and/or (f) unlimited towing when the propulsion motor is running as a pump. The hydraulic circuit is optionally at least one of the hydrostatic or open-circuit propulsion systems. The hydrostatic propel circuit optionally includes a plurality of motors and pumps, wherein the plurality of motors include at least one of a fixed or variable motor. The open-circuit propel system optionally includes one pump and a plurality of motors, and wherein the motors include at least one of a fixed or variable motor. The accumulator can optionally be a standalone component, or in a charging system with a fixed or variable pump. The normal steering and braking system optionally has a fixed or variable pump.

In accordance with other non-limiting aspects of the present disclosure, the work function actuator can optionally include at least one work motor of a fan drive motor, a generator motor, cylinders, rotary actuators, or any motor that is loaded during engine dynamic braking, and wherein the work motor can be part of a fixed or variable pump system.

In accordance with other non-limiting aspects of the present disclosure, the hydraulic circuit optionally further includes a work function pump configured to be de-stroked to zero displacement, or dump its output to a reservoir, during engine dynamic braking.

In accordance with other non-limiting aspects of the present disclosure, the hydraulic valve manifold that directs the braking energy to all the functions optionally includes any type of hydraulic valve and/or solenoid valve. The braking energy is optionally from the high pressure at the propel motor side when the motor is running as a pump. The motor may run as a pump, for example, when: (a) the engine dies at high machine velocity on flat ground; (b) the engine dies while travelling downhill; (c) the machine is decelerating; and/or, (d) the machine is being towed in forward direction.

In accordance with other non-limiting aspects of the present disclosure, the braking energy can also optionally be from the high pressure at the propel motor side when the motor is running as a pump and the port B (e.g., return line) is blocked between the motor and the pump. In addition, the braking energy can optionally be from pressure at port B on the propel motor side if port A is high pressure when the machine travels forward direction. Furthermore, the braking energy can also optionally be from pressure at port A on the propel motor side if port B is high pressure when the machine travels in a forward direction. The hydraulic circuit optionally further comprises a micro-controller.

In accordance with other non-limiting aspects of the present disclosure, a hydraulic circuit is disclosed which includes a pump configured to be driven by a prime motor, a motor fluidly coupled to the pump by a supply line and a return line, at least one work function circuit fluidly coupled with at least one of the supply and return lines, and valving operative to direct at least a portion of pressurized fluid output from the motor during braking operations to the at least one work function circuit to thereby reduce or prevent the prime motor from over-speeding and/or to minimize heat generation in the hydraulic circuit.

In accordance with other non-limiting aspects of the present disclosure, the hydraulic circuit can optionally be a hydrostatic and/or open machine propel circuit.

In accordance with other non-limiting aspects of the present disclosure, the at least one work function circuit can optionally further include at least one of a work motor and/or a work function pump.

In accordance with other non-limiting aspects of the present disclosure, the work motor can optionally include one of a fan drive motor, a generator motor, cylinders, and/or rotary actuators.

In accordance with other non-limiting aspects of the present disclosure, the work function pump can optionally be configured to be de-stroked to zero displacement and/or to dump its output to a reservoir.

In accordance with other non-limiting aspects of the present disclosure, the hydraulic circuit can optionally further include one or more accumulators configured to be charged by the at least one work function circuit.

In accordance with other non-limiting aspects of the present disclosure, the accumulator can optionally be a standalone component or be included as part of a charging system having a fixed and/or variable pump.

In accordance with other non-limiting aspects of the present disclosure, the at least one work function circuit of the hydraulic circuit can optionally include an engine control circuit configured to minimize over-speeding in the prime motor, assist in acceleration, and/or permit unlimited towing.

In accordance with other non-limiting aspects of the present disclosure, the engine control circuit can optionally include one or more solenoid valves, an orifice, a pressure relief valve, one or more pressure transducers, one or more hydraulic pilot-operated valves, a check valve, a pressure-reducing valve, and combinations thereof.

In accordance with other non-limiting aspects of the present disclosure, the at least one work function circuit of the hydraulic circuit can optionally include a heat control circuit configured to minimize heat generation.

In accordance with other non-limiting aspects of the present disclosure, the heat control circuit can optionally have a fan pump and/or a fan drive motor.

In accordance with other non-limiting aspects of the present disclosure, the at least one work function circuit of the hydraulic circuit can optionally further include a braking energy circuit configured to control emergency steering and/or braking.

In accordance with other non-limiting aspects of the present disclosure, the braking energy circuit can optionally have a steering circuit control, a braking circuit control, and/or a hydraulic valve manifold configured to direct braking energy.

In accordance with other non-limiting aspects of the present disclosure, there is provided a hydrostatic propulsion system in a machine. The system includes a hydraulic circuit which can have a pump configured to be driven by an engine, a motor fluidly coupled to the pump by a supply line and a return line, the motor including a high-pressure port side and being configured to run as a pump. The system can also include a pressurized fluid output from the motor during a deceleration of the machine and at least one work function circuit fluidly coupled with at least one of the supply and return lines. The at least one work function circuit can include an engine control circuit configured to minimize over-speeding in the engine, assist in acceleration, and/or permit unlimited towing. The high-pressure port side of the motor can be configured to direct a braking energy generated from the deceleration to the at least one work function circuit.

In accordance with other non-limiting aspects of the present disclosure, the system can optionally further include one or more operating conditions in which the motor runs as a pump. The one or more operating conditions include, but are not limited to: the engine dying when the machine is operating at a high velocity on flat ground; the engine dying when the machine is travelling downhill; machine deceleration; the machine is being towed in a forward direction; a port of the return line being blocked between the motor and the pump; and/or the machine is traveling in a forward direction.

In accordance with other non-limiting aspects of the present disclosure, the at least one work function circuit of the system can optionally further include a heat control circuit configured to minimize heat generation.

In accordance with other non-limiting aspects of the present disclosure, the at least one work function circuit can optionally include a braking energy circuit configured to control emergency steering and/or braking and which can include one or more accumulators.

In accordance with other non-limiting aspects of the present disclosure, there is provided a method of controlling a hydraulic drive of a machine. The hydraulic drive includes a pump adapted to be driven by an engine of the machine, a motor fluidly coupled to the pump by a supply line and a return line and including a high-pressure port side, and at least one work function circuit fluidly coupled with at least one of the supply and return lines. The method can include directing at least a portion of a pressurized fluid output from the high-pressure port side of the motor to the at least one work function circuit and, returning the pressurized fluid back to the high-pressure port side of the motor when the motor is running as a pump; wherein the directing and returning prevents over-speeding in the prime motor and/or minimizes heat generation in the hydraulic drive.

In accordance with other non-limiting aspects of the present disclosure, the method can optionally further include one or more of: assisting in accelerating the machine; permitting unlimited towing of the machine; emergency steering and braking of the machine; and/or charging one or more accumulators. The assisting of the accelerating, the permitting of the unlimited towing, the emergency steering and braking, and/or the charging of one or more accumulators is being performed by the directing of the pressurized fluid to the at least one work function circuit.

In accordance with other non-limiting aspects of the present disclosure, the returning of the pressurized fluid back to the high-pressure port side of the motor when the motor is running as a pump can optionally occur when the engine dies while the machine is operating at a high velocity on flat ground, the engine dies while the machine is travelling downhill, the machine decelerates, the machine is being towed in a forward direction, a port of the return line is blocked between the motor and the pump, and/or the machine is traveling in a forward direction.

These and other objects and advantages will become apparent from the discussion of the distinction between the present disclosure and the prior art and when considering the non-limiting embodiments of the disclosure as shown in the accompanying drawings.

1 FIG. 100 100 104 112 120 112 104 102 102 104 112 110 118 112 Referring now in greater detail to the drawings, wherein the showings are for the purpose of illustrating non-limiting embodiments of the invention only and not for the purpose of limiting the invention,illustrates a typical prior art closed-loop hydrostatic propulsion system. The systemgenerally includes a hydrostatic pumpfluidly coupled to one or more hydrostatic motor(s)forming a main hydraulic loop. The hydrostatic motor(s)can be fixed or variable. The pumpis typically connected to a prime motor, such as an internal combustion engine or the like, of a machine or vehicle. The prime motordrives the pumpto deliver hydraulic fluid to the motorvia supply/return lines/. The motordrives one or more wheels, tracks, etc. to propel the vehicle.

114 104 112 112 104 106 120 122 108 116 112 104 112 104 A valve(electric proportional/on-off, or hydraulic proportional/on-off, or manual proportional/on-off, or non-servo direct displacement control) inside the pumpcontrols the speed and direction of the motorby modulating flow rate and changing flow direction supplied to the motorby the pump. A charge pumpreplenishes the main hydraulic loopwith cool and clean hydraulic fluid from a sump (reservoir). High pressure relief valves/provide overpressure protection for the main hydraulic loop. The machine is designed to travel forward when port A of the motorand the pumpis high pressure, and travel in reverse when port B of the motorand the pumpis high pressure.

104 112 104 104 102 102 104 When moving in a forward direction and the machine begins to decelerate (i.e., when the machine shifts to a “braking mode”), pumpde-strokes toward 0 degrees and Port A pressure drops, and port B pressure increases. In braking mode, the motorgathers the vehicle's momentum and runs as a pump, while pumpruns as a motor. The input torque from the pumptransfers to the prime motor(i.e., the machine's engine) and can cause overspeed in the engine due to insufficient engine braking power. The more input torque, the more engine overspeed. Excessive overspeed may damage the engineand the pump.

112 104 104 Higher pressure on port B at the motorside provides sufficient braking torque to stop the machine. Lower pressure on port B at the pumpside reduces the input torque from the pumpto the engine and avoids excessive engine overspeed.

There is typically little or no engine overspeed risk during machine deceleration when operating in the reverse direction because the maximum reverse speed is normally much slower.

2 FIG. 1 FIG. 2 FIG. 200 100 200 204 228 212 204 202 204 212 210 218 214 204 212 212 204 206 228 232 208 216 illustrates a prior art closed-loop hydrostatic systemwith a similar configuration to the hydraulic circuitof. That is, the closed-loop hydrostatic propulsion systemofincludes a hydrostatic pump, a main hydraulic loop, and one or more hydrostatic motor(s). The pumpis connected to the prime motorof a machine or vehicle. The prime motor drives the pumpto deliver hydraulic fluid to the motorvia supply/return lines/. A valveinside the pumpcontrols the speed and direction of the motorby modulating flow rate and changing flow direction supplied to the motorby the pump. A charge pumpreplenishes the main hydraulic loopwith cool and clean hydraulic fluid from a sump (reservoir). High pressure relief valves/provide overpressure protection for the main hydraulic loop.

200 100 228 230 230 220 222 226 226 224 2 FIG. 1 FIG. The prior art closed-loop hydrostatic systemillustrated indiffers from systemofin that the main hydraulic loopincludes a speed limiter circuitfor preventing engine overspeed. The speed limiter circuitincludes a pilot pressure relief valve, a bypass orifice, and a pressure-reducing valve. Excessive hydrostatic power is converted to heat by the pressure-reducing valve. The heat energy is then dissipated to the ambient environment through the transmission housing or via an associated hydraulic fluid cooler. Bypass check valveis for free flow when the machine travels in reverse.

200 230 204 200 230 2 FIG. During operation of a machine which utilizes a closed-loop hydrostatic system having a speed limiter circuit, such as systemand speed limiter circuitillustrated in, the speed limiter circuit functions to automatically limit the pump torque input to the engine. This may occur when, for example, the pumpis being driven as a motor during vehicle deceleration. Accordingly, when the systemis in braking mode, the hydrostatic motor side may have a port B pressure of about 510 bar, for example. The speed limiter circuitcould then function to limit the pump side pressure of port B to some lower pressure such as about 170 bar, for example.

Non-limiting aspects of the present disclosure are directed to a system (and method) that uses the braking energy of a hydraulic propel system for emergency steering, braking, and/or charging accumulator(s) when the engine dies at high machine velocity on flat ground, when the engine dies while the machine travels downhill, for work functions to minimize heat generation and engine over-speed during machine deceleration, for assisting acceleration, and/or for unlimited towing and limited steering during towing.

Non-limiting aspects of the present disclosure can be used in connection with a wide range of hydraulic circuits to direct braking energy to run emergency steering, braking and/or charge accumulator(s) in the event the prime motor (engine) dies. Certain non-limiting embodiments include propel systems with one or pumps and one or more motors. The motor(s) can be fixed and/or variable.

Non-limiting aspects of the present disclosure can be implemented in a wide variety of hydraulic drive systems or other hydraulic circuits and methods. In particular, certain aspects are directed to circuit designs that direct braking energy to any type of work function actuators (e.g., cylinders, rotary actuators, etc.) that are loaded, such as a fan motor and/or a generator motor, etc. in a fixed or variable pump system, open-circuit or closed-loop hydrostatic. The work function pump (if present) either dumps its output to a reservoir or de-strokes to 0 degrees during machine deceleration.

Non-limiting aspects of the present disclosure can be implemented in a wide variety of hydraulic circuit designs and, in particular, certain aspects are directed to circuit designs wherein a valve manifold directs the braking energy to functions using any type and/or combination of hydraulic valves and/or solenoid valves.

3 3 FIGS.A andB 300 300 304 312 304 300 304 312 310 318 Referring now to, an exemplary hydraulic circuitin accordance with the present disclosure is illustrated. The exemplary hydraulic circuitgenerally includes a hydrostatic pumpand one or more hydrostatic motor(s). The pumpis connected to a prime motor (not shown) of a machine or vehicle. The prime motor of a machine or vehicle as disclosed herein may be, for example, a hydrostatic transmission of the hydrostatically-driven vehicle such as, for example, a forklift truck or construction machinery. However, this aspect is non-limiting and other types of vehicles or machines can be used with exemplary hydraulic circuit. The prime motor drives the pumpto deliver hydraulic fluid to the motorvia first and second lines (i.e., supply/return lines/).

3 3 FIGS.A andB 300 In the embodiment illustrated in, the braking energy is utilized for emergency steering, braking, charging accumulator(s), and/or one or more of work functions (hydraulic actuators) to minimize heat generation, minimize engine overspeed, assisting acceleration and/or assisting unlimited towing. More particularly, circuitincludes one or more dedicated work function circuits configured to perform one or more of the aforementioned tasks. Generally, each dedicated work function circuit can include one or more work function actuators and/or one or more work function pumps. The function actuators are typically a work motor; however, such a configuration is non-limiting. Exemplary work motors include but are not limited to fan drive motors, generator motors, cylinders, rotary actuators, and/or any motor that is loaded during engine dynamic braking.

300 319 319 319 320 338 322 324 326 328 330 332 334 336 3 FIG.A In one non-limiting configuration, hydraulic circuitincludes a work function circuitconfigured to minimize engine overspeed, assist in acceleration, and permit unlimited towing (i.e., engine control circuit). As illustrated in, the engine control circuitgenerally includes one or more solenoid valves/, orifice, relief valve, one or more pressure transducers/, one or more hydraulic pilot-operated valves/, check valve, and pressure reducing valve. However, such a configuration is non-limiting.

300 339 339 339 340 342 344 346 348 3 FIG.A In another non-limiting configuration, hydraulic circuitcan further include work function circuitconfigured to minimize heat generation (i.e., heat control circuit). As illustrated in, the heat control circuitis generally a fixed displacement pump system that includes fan pump, solenoid valve, check valve, fan drive motor, and 4-way valve. However, such a configuration is non-limiting.

300 349 349 350 352 354 356 358 350 352 358 349 356 350 352 339 319 3 FIG.B In additional non-limiting configurations, hydraulic circuitcan also include a braking energy circuitconfigured to control emergency steering and braking as well as accumulator(s) charging. As illustrated in, the braking energy circuitgenerally includes steering control circuit, braking control circuit, solenoid valve, accumulator(s), and hydraulic valve manifold. However, such a configuration is non-limiting. The steering control circuitand braking control circuitcan optionally include one or more fixed or variable pumps. The hydraulic valve manifoldof the braking energy circuittypically includes any number of different types of hydraulic valves and/or solenoid valves which can be configured to direct the braking energy to each of the dedicated work functions, such as charging accumulator(s), enabling steering and braking by control circuits/, powering heat control circuit, and enabling engine control circuit. However, such a configuration is non-limiting.

300 319 339 349 Moreover, the hydraulic circuitand each of the dedicated work function circuits (e.g., engine control circuit, heat control circuit, braking energy circuit) include valving (shown but not numbered) which is generally operative to direct at least a portion of pressurized fluid output from the motor during braking operations to at least one of the one or more work function circuits or accumulators. It should also be appreciated that other types of work functions can additionally or alternatively be powered by the braking energy without departing from the scope of this disclosure.

300 300 312 304 330 332 304 312 312 3 3 FIGS.A andB The exemplary hydraulic circuitillustrated inis advantageously enabled to respond to various states of machine operation. For example, exemplary hydraulic circuitmay operate in response to machine operation states such as: when the engine dies at high machine velocity on flat ground; when the engine dies while the machine travels downhill; during machine deceleration; when the machine is being towed; and/or any other situation when motoris running as a pump and the pumpis running as a motor. During these situations, port B pressure goes up, and port A pressure goes down. The hydraulic pilot-operated valvesandshift when port B pressure reaches a certain predetermined value (e.g., 50 bar, 75 bar, 45 bar, etc.). By blocking port B between the pumpand the motor, the braking energy from high-pressure port B at the motorside is transferred to the various other work functions (e.g., transferred to run steering, braking, charging accumulator(s), etc.).

300 336 356 356 328 342 338 340 360 342 346 348 344 340 During operation of exemplary hydraulic circuit, the pressure-reducing valvesetting determines the pressure to which the accumulatoris charged. When the accumulatoris fully charged, the micro-controller (not shown) receives a signal from the pressure transducerand energizes the solenoid valvesand. The fan pumpdumps hydraulic fluid to reservoirvia solenoid valve. The braking energy is directed to run the fan motorvia a 4-way valve. The check valveblocks fluid from back flowing into the fan pump.

The exemplary micro-controller (not-shown) described herein can include a processor for operating software logic and can be connected to a plurality of sensors which detect various characteristics of the hydraulic circuit. For example, sensors can be positioned to detect engine load, system speed, differential pressures, etc.

346 304 360 304 The return hydraulic fluid from the fan motorgoes back to port B at the pumpside and/or the reservoir. This minimizes input torque from the pumpto the engine, preventing or reducing engine overspeed.

324 Excess hydraulic fluid goes through the relief valveto the low side of the loop. This minimizes heat generation in the system.

312 In use, if the engine dies at machine high velocity on flat ground or if the engine dies when the machine travels downhill, the braking energy provides pressurized hydraulic fluid from the high-pressure port B of the motorfor emergency steering and/or braking while charging the accumulator(s) at the same time.

322 324 304 332 An orificeand the relief valvedetermine how much of the braking power is converted to heat, with the rest being the input power from the pumpto the engine if the valvegets stuck in a blocking position.

312 346 344 348 346 346 It should be appreciated that the hydrostatic braking power of the machine is not negatively influenced by the features of the present disclosure. During use, the motoralways records the maximum braking pressure as if the features don't exist. Only the fan motor, the check valveand the 4-way valveare exposed to the maximum braking pressure during engine dynamic braking. As such, they should be rated to the maximum braking pressure. The braking energy may also make the fan motorrun faster than normal speed. Accordingly, the system design should account for the fan motormaximum speed to remain within its limits when subjected to maximum braking pressure.

320 338 304 312 346 356 356 336 When the machine travels in reverse direction, the solenoid valveis energized and the valveis de-energized. Port B is high pressure. During this operation, the port B between the pumpand the motoris connected. Port B is blocked from fan drive motorand from the accumulatorafter the accumulatoris fully charged to the pressure-reducing valvesetting.

320 338 304 312 356 346 326 354 356 354 When the machine accelerates in a forward direction, the solenoid valveis energized and the valveis de-energized. Port B is low pressure and is connected between the pumpand the motor. The port B is blocked from accumulatorand fan drive motor. If the machine does not have sufficient horse power to accelerate, or if an acceleration boost is desired, port A pressure drops to below a certain value (e.g., 200 bar or any other value), the micro-controller (not shown) receives a signal from the pressure transducerand energizes the solenoid valve, the accumulatordischarges energy to assist acceleration until it is fully discharged, then the solenoid valveis de-energized.

312 330 332 312 354 304 When the machine is being towed in a forward direction, the motorruns as a pump. The high pressure at port B shifts hydraulic pilot-operated valvesand. Port A and port B of the motorare connected when the solenoid valveis manually overridden. The towing is unlimited because the pumpis bypassed.

356 356 304 312 If the accumulator(s)is fully charged before the towing, the steering function can be run to discharge the accumulator(s). The steering is limited because the return hydraulic fluid from the steering is draining out of the loop. It may cause damage to the pumpand motorwhen there is not sufficient hydraulic fluid in the loop. In any case, there typically is not much need for steering during towing and this will not affect the unlimited towing.

356 356 3 3 FIGS.A andB 3 3 FIGS.A andB It should be appreciated that the accumulator, as illustrated in, is shown as being included with a charging system. However, such a configuration is non-limiting. For example, the accumulator could also be provided as a standalone component. Moreover, the accumulatorinis illustrated as part of a charging system with one or more fixed pumps. However, this is non-limiting, and it should be understood that the charging system and accumulator could also utilize one or more variable pumps, or a combination of fixed and variable pumps, without departing from the scope of the present disclosure.

4 4 FIGS.A andB 4 FIG.B 4 FIG.A 400 400 404 420 412 404 402 404 412 410 418 414 404 412 412 404 406 420 422 408 416 Referring now to, an exemplary hydraulic propel systemin accordance with the present disclosure is shown including a hydraulic fan drive system with an electronic diesel control (“EDC”) pump.is a simplified version of, and like reference numerals have been used to identify identical components. The exemplary hydraulic propel systemincludes a hydrostatic pump, a main hydraulic loop, and one or more hydrostatic motor(s). The pumpis connected to the prime motorof a machine or vehicle. The prime motor drives the pumpto deliver hydraulic fluid to the motorvia supply/return lines,. A valveinside the pumpcontrols the speed and direction of the motorby modulating flow rate and changing flow direction supplied to the motorby the pump. A charge pumpreplenishes the main hydraulic loopwith cool and clean hydraulic fluid from a sump (reservoir). High-pressure relief valves,provide overpressure protection for the main hydraulic loop.

400 423 423 423 426 434 424 428 432 4 4 FIGS.A andB In one non-limiting configuration, hydraulic propel systemincludes a work function circuitconfigured to minimize engine overspeed (i.e., engine control circuit). As illustrated in, the engine control circuitgenerally includes one or more solenoid valves,, orifice, relief valve, and one or more pressure transducers. However, such a configuration is non-limiting.

400 435 435 435 436 438 440 4 4 FIGS.A andB In another non-limiting configuration, hydraulic propel systemcan further include work function circuitconfigured to minimize heat generation (i.e., heat control circuit). As illustrated in, the heat control circuitis generally a variable displacement pump system that includes fan pump, fan drive motor, and check valve. However, such a configuration is non-limiting.

426 434 436 432 444 446 435 412 438 448 440 438 404 428 404 402 During engine dynamic braking, the micro-controller (not shown) shifts solenoid valvesandand de-strokes the fan pumpto 0 degrees when pressure transducermeasures port B pressure higher than a predetermined value (e.g., 25 bar, etc.). High-pressure relief valves,provide overpressure protection for the variable fan pump system (i.e., heat control circuit). The hydraulic fluid at propel motorside is directed to the fan motorand 4-way valveonly due to check valve. The return fluid from the fan motorgoes back to the port B at propel pumpside at a reduced pressure. The excessive hydraulic fluid goes through the relief valveto the low side of the loop. This minimizes heat and input torque from the pumpto the engine.

424 428 404 402 434 The orificeand relief valvedetermine how much of the braking power is converted to heat. The remaining braking power is input from the pumpto the engine, but only if solenoid valvefails.

412 438 448 440 438 438 It should be appreciated that the hydrostatic braking power of the machine is not negatively influenced by the features of the present disclosure. During use, the motoralways records the maximum braking pressure as if the features don't exist. Only the fan motor, the 4-way valve, and check valveare exposed to the maximum braking pressure during engine dynamic braking. These components should be rated to the maximum braking pressure. The braking energy may also make the fan motorrun faster than normal speed. Accordingly, system design should account for the fan motormaximum speed to remain within its limits when subjected to maximum braking pressure.

5 FIG. 5 FIG. 4 FIG. 500 500 400 500 400 500 504 512 504 504 522 512 510 518 Referring now to, an exemplary hydraulic propel systemin accordance with the present disclosure is shown. Systemillustrated inis substantially similar to systemillustrated in. However, systemis a fixed pump fan drive system in accordance with the present disclosure, as opposed to the variable pump system. The exemplary hydraulic propel systemincludes a hydrostatic pumpand one or more hydrostatic motor(s). The pumpis connected to the prime motor (not shown) of a machine or vehicle. The prime motor drives the pumpto deliver hydraulic fluid from a sump (reservoir)to the motorvia supply/return lines,.

500 523 523 523 526 534 524 528 532 5 FIG. In one non-limiting configuration, hydraulic propel systemincludes a work function circuitconfigured to minimize engine overspeed (i.e., engine control circuit). As illustrated in, the engine control circuitgenerally includes one or more solenoid valves,, orifice, relief valve, and one or more pressure transducers. However, such a configuration is non-limiting.

500 535 535 535 536 538 540 5 FIG. In another non-limiting configuration, hydraulic propel systemcan further include work function circuitconfigured to minimize heat generation (i.e., heat control circuit). As illustrated in, the heat control circuitis generally a fixed pump system that includes fan pump, a solenoid valve, and a fan drive motor. However, such a configuration is non-limiting.

526 534 536 522 538 532 544 546 535 512 540 548 542 540 504 528 504 During engine dynamic braking, the micro-controller (not shown) shifts solenoid valves,and dumps fan pumpto reservoir, via solenoid valve, when pressure transducermeasures port B pressure higher than a predetermined value (e.g., 25 bar, etc.). High pressure relief valves,provide overpressure protection for the fixed fan pump system (i.e., heat control circuit). The hydraulic fluid at propel motorside is directed to the fan motorand 4-way valveonly due to check valve. The return hydraulic fluid from fan motorgoes back to port B at propel pumpside at a reduced pressure. The excessive hydraulic fluid goes through the relief valveto the low side of the loop. This minimizes heat and input torque from the pumpto the engine.

524 528 504 534 The orificeand relief valvedetermine how much of the braking power is converted to heat. The remaining braking power is input from the pumpto the engine if the valvegets stuck in blocking position.

512 538 548 542 538 438 It should be appreciated that the hydrostatic braking power of the machine is not negatively influenced by the features of the present disclosure. During use, the motoralways records the maximum braking pressure as if the features don't exist. Only the fan motor, the 4-way valve, and check valveare exposed to the maximum braking pressure during engine dynamic braking. They should be rated to the maximum braking pressure. The braking energy may also make the fan motorrun faster than normal speed. Accordingly, system design should account for the fan motormaximum speed to remain within its limits when subjected to maximum braking pressure.

6 6 FIGS.A andB 6 FIG.A 600 600 600 619 619 619 620 638 622 624 626 628 634 636 Referring now to, there is illustrated a non-limiting exemplary embodiment of hydraulic circuitin accordance with aspects of the present disclosure. In this embodiment, braking energy is utilized for an accumulator charging system and emergency steering and braking. More particularly, circuitincludes one or more dedicated work function circuits configured perform the aforementioned tasks. In one non-limiting configuration, hydraulic circuitincludes a work function circuitconfigured to minimize engine overspeed, assist in acceleration, and permit unlimited towing (i.e., engine control circuit). As illustrated in, the engine control circuitgenerally includes one or more solenoid valves,, orifice, relief valve, one or more pressure transducers,, check valve, and pressure-reducing valve. However, such a configuration is non-limiting.

600 649 649 650 652 654 656 658 650 652 658 649 656 650 652 619 6 FIG.B In another non-limiting configuration, hydraulic circuitcan also include a braking energy circuitconfigured to control emergency steering and braking as well as accumulator(s) charging. As illustrated in, the braking energy circuitgenerally includes steering control circuit, braking control circuit, solenoid valve, accumulator(s), and hydraulic valve manifold. However, such a configuration is non-limiting. The steering control circuitand braking control circuitcan optionally include one or more fixed and/or variable pumps. The hydraulic valve manifoldof the braking energy circuittypically includes any number of different types of hydraulic valves and/or solenoid valves which can be configured to direct the braking energy to each of the dedicated work functions, such as charging accumulator(s), enabling steering and braking by control circuits/, and/or enabling engine control circuit. However, such a configuration is non-limiting.

600 619 649 Moreover, the hydraulic circuitand each of the dedicated work function circuits (e.g., engine control circuitand braking energy circuit) include valving (shown but not numbered) which is generally operative to direct at least a portion of pressurized fluid output from the motor during braking operations to at least one of the one or more work function circuits or accumulators. It should also be appreciated that other types of work functions can additionally or alternatively be powered by the braking energy without departing from the scope of this disclosure.

600 600 612 604 6 6 FIGS.A andB The exemplary hydraulic circuitillustrated inis advantageously enabled to respond to various states of machine operation. For example, exemplary hydraulic circuitmay operate in response to machine operation states such as: when the engine dies at high machine velocity on flat ground; when the engine dies while the machine travels downhill; during machine deceleration; when the machine is being towed; and/or any other situation when motoris running as a pump and the pumpis running as a motor. During these situations, port B pressure goes up, and port A pressure goes down.

600 636 656 656 628 620 638 604 612 612 During operation of exemplary hydraulic circuit(i.e., during dynamic engine braking) the pressure-reducing valvesetting determines the pressure to which the accumulatoris charged. When the accumulatoris fully charged, the micro-controller (not shown) receives a signal from the pressure transducerand shifts solenoid valvesand. The signal can report that port B pressure is higher than a set value (e.g., 25 bar). By blocking port B between the pumpand the motor, the braking energy from high-pressure port B at the motorside is transferred to the various other work functions (e.g., transferred to run steering, braking, charging accumulator(s), etc.).

604 660 604 624 612 656 The return hydraulic fluid from the other work function circuits goes back to port B at the pumpside and/or the reservoir. This minimizes input torque from the pumpto the engine, preventing or reducing engine overspeed. Excess hydraulic fluid goes through the relief valveto the low side of the loop. This minimizes heat generation in the system. In use, if the engine dies at machine high velocity on flat ground or if the engine dies when the machine travels downhill, the braking energy provides pressurized hydraulic fluid from the high-pressure port B of the motorfor emergency steering and/or braking while charging the accumulator(s)at the same time.

622 624 604 638 An orificeand the relief valvedetermine how much of the braking power is converted to heat, with the rest being the input power from the pumpto the engine if the valvegets stuck in blocking position.

620 638 604 612 656 656 636 When the machine travels in reverse direction, the solenoid valveis energized and the valveis de-energized. Port B is high pressure and is connected between the pumpand the motor. Port B is blocked from the accumulatorafter the accumulatoris fully charged to the pressure reducing valvesetting.

620 638 604 612 656 626 654 656 654 When the machine accelerates in forward direction, the solenoid valveis energized and the valveis de-energized. Port B is low pressure and it connected between the pumpand the motor. Port B is blocked from accumulator. If the machine does not have sufficient horse power to accelerate, or if acceleration boost is desired, port A pressure drops to below a predetermined value (e.g., 200 bar or any other value), the micro-controller (not shown) receives a signal from the pressure transducerand energizes the solenoid valve, the accumulatordischarges energy to assist acceleration until it is fully discharged, then the solenoid valveis de-energized.

612 620 638 612 654 604 When the machine is being towed in forward direction, the motorruns as a pump. The high pressure at port B shifts solenoid valvesand. Port A and port B of the motoris connected when the solenoid valveis manually overridden. The towing is unlimited because the pumpis bypassed.

656 656 604 612 If the accumulator(s)is fully charged before the towing, the steering function can be run to discharge the accumulator(s). The steering is limited because the return hydraulic fluid from the steering is draining out of the loop. It may cause damage to the pumpand motorwhen there is not sufficient hydraulic fluid in the loop. In any case, there typically is not much need for steering during towing and this will not affect the unlimited towing.

656 656 6 6 FIGS.A andB 6 6 FIGS.A andB It should be appreciated that the accumulator, as illustrated in, is shown as being included with a charging system. However, such a configuration is non-limiting. For example, the accumulator could also be provided as a standalone component. Moreover, the accumulatorinis illustrated as part of a charging system with one or more fixed pumps. However, this is non-limiting, and it should be understood that the charging system and accumulator could also utilize one or more variable pumps, or a combination of fixed and variable pumps, without departing from the scope of the present disclosure.

It should now be appreciated that, in view of the various non-limiting embodiments discussed above, one or more of the following features may be present in a hydraulic circuit according to the system and method disclosed herein. The exemplary propel systems can be hydrostatic systems or open-circuit systems. The hydrostatic propel systems can be 1× pump and 1× motor, 1× pump and more motors, or any numbers of pumps and motors, and the motor(s) can be fixed, 2-position or proportional. The open-circuit propel system can be 1× pump and 1× motor, 1× pump and more motors, or any numbers of pumps and motors, and the motor(s) can be fixed, 2-position or proportional.

While considerable emphasis has been placed herein on the structures and configurations of the preferred embodiments of the disclosure, it will be appreciated that other embodiments, as well as modifications of the embodiments disclosed herein, can be made without departing from the principles of the disclosure. These and other modifications of the preferred embodiments, as well as other embodiments of the disclosure, will be obvious and suggested to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the present disclosure and not as a limitation thereof.